EMF is an unfortunate term because volts are not units of force.

 

EMF is an unfortunate term because volts are not units of force.

Perhaps not strictly, but it's a convenient way to visualize how volts cause current through an impedance.

 

Well if you are accustomed to thinking of volts as a force then you will not be able to reconcile that the energy stored in a capacitor is 0.5*C*V^2, nor a lot of other important physical concepts. If one needs to visualize a force then that is the role of the E-field. Like any other skill, electronics should start with solid fundamentals, shouldn't it?

 

Well if you are accustomed to thinking of volts as a force then you will not be able to reconcile that the energy stored in a capacitor is 0.5*C*V^2, nor a lot of other important physical concepts. If one needs to visualize a force then that is the role of the E-field. Like any other skill, electronics should start with solid fundamentals, shouldn't it?

I don't see how viewing voltage as a force makes it impossible to understand the energy in a capacitor is 1/2 CV².
The electrons are stuffed into the capacitor with a force (similar to pushing a spring). That gives energy to the electrons that is recovered when they are pushed back out by the voltage "force". You can look at the force as tiny electric field "springs" between the electrons.

True, the E field generates the force but the voltage is a measure of the E field so I think a little slop between the two is not a big deal.

Do you think the math somehow doesn't work if you view voltage as a force?
If so, why?

I appreciate the "solid fundamentals" but you don't have to be dogmatic about them to understand electronics.

 

another wy to think about it:
http://www.sengpielaudio.com/ohms-law-illustrated.gif

 

I like the Stone Rolling Down hill analogy which is:

Voltage = Speed of stone
Current = Size of stone
Resistance = bush on the hill that slows the stone down

 

This is a mechanical analogy that's a little more abstract than hydraulic systems but it's less likely IMO to lead to confusion on charge vs energy and it might be related to the origin of the somewhat archaic term of electrical 'high' tension that survives today.

 

EMF is an unfortunate term because volts are not units of force.

Voltage is not a force that causes the electrons to move? Static electricity that causes things to move is not a force? What am I missing?

 

Well if you are accustomed to thinking of volts as a force then you will not be able to reconcile that the energy stored in a capacitor is 0.5*C*V^2, nor a lot of other important physical concepts. If one needs to visualize a force then that is the role of the E-field. Like any other skill, electronics should start with solid fundamentals, shouldn't it?

For those who only play with electronics for curiosity and are not engineers your descriptions add to the confusion.. Save the engineering for engineers, please. You are most correct, of course. But beginners may not need it.

 

I like the Stone Rolling Down hill analogy which is:

Voltage = Speed of stone
Current = Size of stone
Resistance = bush on the hill that slows the stone down

Voltage = gravity ??? The force causing the motion.

 

Voltage = gravity ??? The force causing the motion.

I would agree.
Gravity = voltage
Stone inertia (size) = inductance
Bush =resistance
Stone speed = current

 

I decided to stop with analogies and try to understand things in its own terms. Mental stunts started to be tiring for me.

Yesterday the water, now the ball downhill. No, thanks.

 

For those who only play with electronics for curiosity and are not engineers your descriptions add to the confusion.

Wrong. Unless a person is absolutely determined to remain perpetually ignorant and never learn anything, those things add to knowledge and understanding, not to confusion, even though they may be a bit difficult to grasp at first.

Save the engineering for engineers, please.

No.

You're welcome to promote ignorance if you want, but I prefer to promote knowledge-- especially for hobbyists, because I learned a long time ago that the amount of fun you have with electronics is directly proportional to how well you understand the fundamentals. Electronics is a lot more fun when you can do more than blindly copy what others have created.

You are most correct, of course. But beginners may not need it.

They sure as hell do need it, if they ever want to be anything other than a beginner.

 

When dealing with the unknown, we all need to start with something. We must have some sort of reference related to something that we're familiar with, or things become much more difficult to understand.

To me, it's exactly like learning another language. Of course, most languages share ethymologies in some words. But when it comes to grammar and the structure of ideas, it's an entirely different ball game.
Eventually one has to abandon thinking in ways of one's mother language, and embrace the new one on its own terms.

Learning electronics has been the same for me.

 

Well said.

 

E = 0.5*C*V^2

Do you think the math somehow doesn't work if you view voltage as a force?
If so, why?

It's just algebra. If you interchange units of force for volts then you end up with units of force for energy, which is clearly wrong. The energy stored in a capacitor is not x Newtons, it is x Joules. You won't get the correct units for energy unless you put the correct definition/units in for volts, which is Joules per Coulomb. Knowing the difference between Newtons and Joules is not arcane knowledge reserved for engineers and scientists, it is something anyone that wants some fundamental understanding of the hobby should know. One doesn't have to aspire to be the next Shakespear to understand the importance of learning the alphabet - before they start reading and writing. Starting out with the wrong definitions means one is building a foundation that is a conceptual house of cards.

I remember someone coming to this forum, very confused. He had a very simple circuit, a closed balanced DC circuit with no current flowing and he had a very good question. He asked how come I measure 5V of force at this point in the circuit, in a conductor, and yet there is no current flowing. And then he went to the water pipe analogy to show why there should be current flowing. "What am I getting wrong here?" So then I had to explain that volts are not units of force and that point in the circuit had no current flowing because there was no E-field in the wire. And I had too re-school him on fundamental definitions of E-fields, potential energy, Volts, etc. and then try to draw a tighter, more helpful, analogies to the water pipe, bla bla bla. All unecessary if he had been taught from the beginning the proper definitions and concepts.

 

It's just algebra. If you interchange units of force for volts then you end up with units of force for energy, which is clearly wrong. The energy stored in a capacitor is not x Newtons, it is x Joules. You won't get the correct units for energy unless you put the correct definition/units in for volts, which is Joules per Coulomb. Knowing the difference between Newtons and Joules is not arcane knowledge reserved for engineers and scientists, it is something anyone that wants some fundamental understanding of the hobby should know. ..........................
I remember someone coming to this forum, very confused. He had a very simple circuit, a closed balanced DC circuit with no current flowing and he had a very good question. He asked how come I measure 5V of force at this point in the circuit, in a conductor, and yet there is no current flowing. And then he went to the water pipe analogy to show why there should be current flowing. "What am I getting wrong here?" ..................

From Wikipedia:
One volt is defined as the difference in electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points.[2] It is also equal to the potential difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it.

Notice that one of the definitions involves newtons.

As far as the water analogy, he apparently wasn't using the analogy incorrectly. You can have pressure in a pipe without water flow, just as you can have voltage in a circuit without current flow.

 

Notice that one of the definitions involves newtons.

One of the definitions of an automobile involves wheels, that doesn't make a car a wheel.

 

One of the definitions of an automobile involves wheels, that doesn't make a car a wheel.

That really clarifies your argument.
But I'm through here.
You can stick with your pedantic view and I'l stay with my less than rigorous one.
It got me through 45 years of electronic design work without a problem.

 

Well seeing as everyones still here there is one thing I want to clarify as I´m about to start chapter 3 in the DC Electronics Textbook. The difference between Joules and Watts is merely a time constraint yes? If this is so, I need help understanding how Joules and Newtons relate to one another. Being that One Newton of force is the force required to accelerate an object with a mass of 1 kilogram 1 meter per second per second. And a Joule It is equal to the energy transferred (or work done) to an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre. Where does the time componet go to? I know the difference between Joules and Watts but not how to reconsle Joules and Newtons. Moreover, is there an equation that relates Newtons and Watts? Sorry for all the questions.